Conventionally known methods for producing coumarin derivatives include, for example, a process in which a hydrogenation-dehydrogenation catalyst, such as palladium, etc., and a 3-(2-cyclohexanoyl)propionic acid ester derivative as a starting material are first introduced into a reactor at a time, and ring formation and dehydrogenation reaction is then conducted with heating, as described in U.S. Pat. No. 3,442,910, and a process in which the ring formation and dehydrogenation reaction for producing a coumarin derivative is performed in the co-presence of a noble metal catalyst, such as palladium, etc., and a promoter such as barium sulfate, nickel oxide, etc., as described, e.g., in JP-A-60-181082. The term "JP-A" as used herein means an "unexamined published Japanese patent application".
However, the conventional processes cannot always produce coumarin derivatives in high yields.